The long term objective of this proposal is to develop a commercial trivalent glycoprotein subunit vaccine for parainfluenza viruses. Because of the high cost of preparing these glycoproteins, a means for achieving an enhanced immune response is an important objective, and is the immediate focus of this proposal. It has been shown that cholera toxin subunit B (CTB) is not only a potent mucosal immunogen but also effective adjuvant for antibody responses to unrelated antigens coadministered. The adjuvanticity of CTB to the PI3 glycoprotein subunit vaccine will be evaluated. Two glycoproteins, fusion (F) and hemagglutin-neuraminidase (HN) proteins, of PI3 virus will be purified from virions or virus infected cells by affinity columns coupled with specific monoclonal antibodies against F or HN. Glycoproteins will be conjugated with CTB by various methods and antigenicity of each component of conjugates as well as the binding activity of conjugated CTB to GM1 ganglioside will be examined. Conjugated or unconjugated glycoproteins will be used for subcutaneous and oral immunization of hamsters and their immune responses will be evaluated. Possibility to use genetically fused CTB and antigen molecules as vaccines will be also examined in Phase II. Finally, the approach will be extended to other paramyxovimses, type 1 and 2, to develop trivalent subunit vaccine.